GENERA OF GRASSES OF THE UNITED STATES. 287 



races of American aborigines, from Peru to middle North America. 

 Several races of corn are grown in the United States, 1 the most im- 

 portant being dent, the common commercial field sort, flint, sweet, and 

 pop. Pod corn (Z. mays tunicata Larr.), occasionally cultivated as a 

 curiosity, is a variety in which each kernel is enveloped in the 

 elongate floral bracts. A variety with variegated leaves (Z. mays 

 japonica Korn.) is cultivated for ornament. 



144. Coix L. 



Spikelets unisexual; staminate spikelets 2-flowered, in twos or 

 threes on the continuous rachis, the normal group consisting of a pair 

 of sessile spikelets with 

 a single pedicellate 

 spikelet between, the lat- 

 ter sometimes reduced 

 to a pedicel or wanting; 

 glumes membranaceous, 

 obscurely nerved; 

 lemma hyaline, nearly 

 as long as the glumes, 

 awnless, 5-nerved ; palea 

 hyaline, a little shorter 

 than the lemma; sta- 

 mens 3 ; pistillate spike- 

 lets 3 together, 1 fertile 

 and 2 sterile at the base 

 of the inflorescence ; fer- 

 tile spikelet consisting 

 of 2 glumes, 1 sterile 

 lemma, a fertile lemma, 

 and a palea ; glumes sev- 

 eral-nerved, hyaline be- 

 low chartaceous in the 



Tipper narrow pointed FIG. 174. Job's-tears, Coix lachryma-jobi. Tipper por- 



part, the first very 



broad, infolding the spikelet, the margins infolded beyond the 2 

 lateral stronger pair of nerves, the second glume narrower than the 

 first, keeled ; sterile lemma about as long as the second glume, similar 

 in shape but a little narrower, hyaline below, somewhat chartaceous 

 above; fertile lemma hyaline, narrow, somewhat shorter than the 

 sterile lemma ; palea hyaline ; narrow, shorter than the lemma ; sterile 

 spikelets consisting of a single narrow tubular glume as long as the 

 fertile spikelet, somewhat chartaceous. 



1 See Montgomery, The Cora Crops, 15, 1913 : Sturtevant, U. S. Dept. Agr., Off. Exp. 

 Sta. Bull. 57. 1899. 



